1. Field of the Invention
The present invention relates to laser systems for medical treatments and in particular, for laser surgical procedures. More particularly, it relates to optical fiber systems and methods used for the treatment of various image guided surgical procedures, such as benign prostatic hyperplasia under echographic imaging.
2. Information Disclosure Statement
Many important medical conditions suffered by many patients require treatments which consist of removing abnormal soft tissue from the body. Undesired tissue may include tumors and atheromatous plaques, excess fat in aesthetic treatments, or portions of prostate tissue. In urology, for example prostate disorders such as cancer or benign enlarged prostate (BPH) require this tissue to be partially or totally removed.
Tissue removal can be performed by means of different methods. Independently of the method used, the main objective of this kind of treatment is the removal of the whole undesired tissue while preventing from damage of surrounding tissue. In recent years, laser energy has been used in order to accomplish this aim.
Based on laser energy application on tissue, numerous approaches have been proposed. Laser techniques are usually preferred due to its special capacity of delivering high amounts of power on reduced areas, thus improving treatment precision and efficiency and diminishing undesired effects on surrounding tissue.
Prostate cancer affects over 232,000 men in the US every year. It is a malignant tumor growth that consists of cells from the prostate gland. The tumor usually grows slowly and remains confined to the gland for many years. During this time, the tumor produces little or no symptoms or outward signs (abnormalities on physical examination). As the cancer advances, however, it can spread beyond the prostate into the surrounding tissues. Moreover, the cancer also can metastasize throughout other areas of the body, such as the bones, lungs, and liver.
Benign prostatic hyperplasia (BPH) or “enlarged prostate” refers to the noncancerous (benign) growth of the prostate gland. While BPH is the most common prostate problem in men over 50 years of age, benign growth of the prostate begins with microscopic nodules around 25 years of age, although it rarely produces symptoms before a man reaches 40. It is estimated that 6.3 million men in the United States have BPH and the disease is responsible for 6.4 million doctor visits and more than 400,000 hospitalizations per year.
The exact cause of BPH is unknown but it is generally thought to involve hormonal changes associated with the aging process. Testosterone likely has a role in BPH as it is continually produced throughout a man's lifetime and is a precursor to dihydrotestosterone (DHT) which induces rapid growth of the prostate gland during puberty and early adulthood. When fully developed, the prostate gland is approximately the size of a walnut and remains at this size until a man reaches his mid-forties. At this point the prostate begins a second period of growth which for many men often leads to BPH later in life.
In contrast with the overall enlargement of the gland during early adulthood, benign prostate growth occurs only in the central area of the gland called the transition zone, which wraps around the urethra. As this area of the prostate grows, the gland presses against the urethra, leading to difficult or painful urination. Eventually, the bladder itself weakens and loses the ability to empty by itself.
Obstructive symptoms such as intermittent flow or hesitancy before urinating can severely reduce the volume of urine being eliminated from the body. If left untreated, acute urine retention can lead to other serious complications such as bladder stones, urinary tract infections, incontinence, and, in rare cases, bladder and kidney damage. These complications are prevalent in older men who are also taking anti-arrhythmic drugs or anti-hypertensive (non-diuretic) medications. In addition to the physical problems associated with BPH, many men also experience anxiety and a reduced quality of life.
Mild symptoms of BPH are most often treated with medication such as alpha-blockers and anti-androgens.
Men suffering with moderate to severe BPH symptoms must typically undergo surgery. There are a number of surgical methods for treatment of BPH. Transurethral resection of the prostate (TURP) has been widely used, but causes a number of complications including bleeding, incontinence, retrograde ejaculation and impotence. An alternative surgical method is transurethral incision of the prostate (TUIP). Incisions are made in the prostate to relieve pressure and improve flow rate. Incisions are made where the prostate meets the bladder. No tissue is removed in the TUIP procedure. Cutting muscle in this area relaxes the opening to the bladder, which decreases resistance to urine flow from the bladder. A variant of the TUIP procedure in which a laser is used to make the incision is the transurethral laser incision of the prostate (TULIP). This method is effective but it's known to cause numerous side effects, including incontinence, impotence, retrograde ejaculation, prolonged bleeding and TURP syndrome.
Photodynamic therapy has also been proposed for treatment of prostatic conditions. For example, Rubinchik et al. disclose in U.S. Patent Publication 2008/0071331A1 a method for treating BPH, comprising the administration of a photosensitizer by direct injection into the prostate tissue of a subject afflicted with or suspected of being afflicted with a prostatic disorder; and irradiation of the prostate tissue with energy at a wavelength appropriate to activate the photosensitizer. Imaging means such as MRI, X-ray, or ultrasound may be used to assess correct placement of injection device. In addition to conventional PDT disadvantages, in this method treatment progress is not assessed by imaging means. As a consequence, treatment precision may be inadequate, thus leading to uncertain results or affecting healthy tissue.
Other surgical techniques used for BPH treatment include methods for causing necrosis of the tissue that blocks the urethra. Hyperthermic methods, for example, use the application of heat to kill unwanted cells, which will gradually be absorbed by the body. Several methods of applying heat or causing necrosis have been used, including direct heat (transurethral needle ablation, or TUNA), ultrasound (high-intensity focused ultrasound, or HIFU), and electrical vaporization (transurethral electrical vaporization of the prostate, or TUEVP). However, the amount of intervention time required to eliminate large amounts of tissue can result in strain and stress on the patient who is usually fully conscious during the intervention. The extensive period of time required is also a cost factor for the operating urologist.
For cancer, when it is detected before metastasis, laser surgery employing side-firing fibers is a preferred treatment among surgeons and patients. It causes little blood loss and allows for a shorter recovery time.
At present, the preferred treatment by those skilled in the art is laser ablation of undesired tissue. There are a number of different laser techniques in which light is used to eliminate excess of prostate tissue either by ablation (vaporization), thermal coagulation or a combination of both these mechanisms. The observed clinical effects are due to the absorption of light (by the target tissue itself and/or surrounding fluids) and subsequent heat transfer, the extent of which largely depends on the power and wavelength of the impinging laser beam.
Most types of laser surgeries are able to provide an immediate improvement in the urinary stream. Laser surgery for BPH has other potential advantages over prior art techniques, such as reduced blood loss as well as shorter treatment times, faster patient recovery, and lower risk of post-treatment incontinence. However, many patients still require catheterization for 1-2 weeks post-treatment after undergoing some forms of laser surgery.
An important factor determining the success of laser surgery in urology is the accuracy with which the surgeon is able to eliminate undesired prostate tissue in order to achieve adequate tissue ablation without damaging surrounding healthy tissue. To accomplish this accuracy, it is necessary to meet at least two requirements: using an appropriate optical fiber and an effective imaging means. Needless to say, laser source should have adequate emission features for performing required treatments.
Regarding optical fibers, inventors have worked over the years on developing diverse optical fiber configurations that can improve efficiency, accuracy and thus safety of the procedure. Fibers must also be able to withstand the high laser energy emitted by new laser source technologies. In BPH treatment, laser beams oriented at a certain angle with respect to the fiber's main axis are preferred. This way, surgeons can limit their lasing to back and forth and rotational movements while they observe the procedure by endoscopy. Several patents disclose different variants of side-firing configurations. Some examples are U.S. Pat. No. 5,292,320 by Brown et al., U.S. Pat. No. 5,509,917 by Cecchetti et al., U.S. Pat. No. 5,366,456 by Rink et al., U.S. Patent Publication 2006/0285798 by Brekke et al., and U.S. Pat. No. 5,416,878 by Bruce.
Recently, Neuberger described in application Ser. No. 12/714,155 a twister fiber, which represents a substantial improvement over prior art, allowing for safer, more accurate and less time consuming procedures. The disclosed device comprises a bent tip fiber with a fused cap as an integral part of it placed at its distal (output) end and with a rotatable connector at the proximal (input) side. Fiber tip may be constructed with different shape configurations, such as a convex tip to improve focusing characteristics, a concave tip to achieve diverging irradiation, or an expanded beam tip to achieve an effect similar to that obtained by electrosurgical tools. A grip guarantees and enhances the ability to twist and rotate it easily. Optical fiber's steerability, twistability and rotation lead to a more precise an improved effect on tissues. Thus, easier, faster and more precise and efficient treatments can be performed. Twister fibers emit light in several directions and carbonization occurs on its surface; most likely in some preferred areas. Since twister fiber is operated in contact-mode, carbonized areas at surface create hot spots that can be used to remove tissue. As a consequence, improved and enhanced treatment of diverse pathologies can be performed, making it possible to efficiently and easily reach and treat specific tissues.
Twister fiber might be inserted, for instance, into an endoscope to perform high power vaporization of prostatic tissue for BPH treatments. Furthermore, it might be steered into one of the prostatic lobes, which might be excavated from the inside in order to relieve pressure on the urethra while maintaining the urethra's integrity as much as possible. Other applications of twister fiber include removal of tumorous (hyperplasic) tissue or other unwanted tissue from the body.
As previously mentioned, in addition to an adequate optical fiber, it is also vital to use an appropriate and effective imaging means in order to achieve a successful treatment. During BPH treatment, field of view may be limited, as the fiber tip is outside cystoscope while endoscopic camera is inside cystoscope. Furthermore, hot spots will cause fiber to enter tissue and therefore, fiber tip will get out of field of view. Other situations may “blind” endoscope lens, such as excessive bleeding, vaporization bubbles and anatomical structures at difficult angles of vision. Thus, endoscopic view may at times result insufficient to continuously monitor the procedure and make sure only unwanted tissue is being ablated. As a consequence, a complementary reliable and noninvasive device and method that can help evaluate tissue damage during laser procedures in real time is needed.
Imaging/control means have been historically used for assessing the amount of tissue damage and for positioning optical fiber. In order to improve tissue damage evaluation and fiber positioning, different approaches have been developed for complementing endoscopy. Some computer modeling techniques intend to predict tissue thermal damage according to different heat transfer theories and knowledge of tissue properties. These methods, without some imaging backup, are still unreliable due to tissue heterogeneity existing in the treated area regarding physical properties, geometry and blood perfusion.
Methods such as thermocouple or light-detector insertion can also provide information about the light distribution or heat development at different points in the tissue. These parameters may be used as feedback tools for laser adjustment during therapy to achieve optimal localized tumor destruction. However, effectiveness is limited because probe insertion is invasive. Furthermore, sites that can be sensed are limited.
Several imaging methods have been proposed to accompany direct endoscopic viewing in order to follow tissue response during laser therapy in medical treatments that require precision to assure treatment efficacy and patient safety. Imaging modalities presently available for the acquisition of clinical images during medical procedures include 2D X-ray imaging, computed tomography, magnetic resonance imaging, 2D radioisotope imaging, single photon emission computed tomography, positron emission tomography, thermography, and transillumination. For example, U.S. Pat. No. 6,684,097 by Parel et al discloses a device for monitoring thermally-induced changes to localized regions of tissue. The device has an X-ray illumination source, an X-ray detector, a data storage unit in communication with the X-ray detector, an image comparison unit and an image display unit in communication with the image comparison unit. The tissue to be monitored is a portion of a patient's body which is being monitored during the surgical procedure. The resultant image signal is a difference image signal that is generated by the image comparison unit and then displayed on an image display unit to provide real-time information concerning the temperature distribution and changes in temperature throughout the portion of the patient's body being monitored. This technology is complex and difficult to apply and requires expensive equipment. Moreover, some of these techniques require considerable processing time before achieving a useful image, thus impeding a real time control of the procedure.
In urologic procedures such as BPH treatment or prostate cancer treatment, ultrasonography has been preferred by those skilled in the art as a practical low-cost and reliable means of identifying essential landmarks and of controlling applied energy action. In medical ultrasound imaging, pulses of longitudinal sound waves at frequencies from 1 to 20 MHz are emitted by one or more piezoelectric transducers into the body volume being imaged. Inside the body, ultrasound is attenuated through scattering and absorption. The intensities and arrival times of ultrasound waves reflected back to the transducer by internal acoustic boundaries are measured and converted into images of the reflecting boundaries. For sound waves, a boundary is a spatial discontinuity in the acoustic impedance, defined in any medium as the product of the speed of sound and density. Speed of sound, and acoustic impedance are temperature dependant.
Some approaches have been proposed for enhancing ultrasound detection of surgical devices inserted into the body. For example, Fry in U.S. Pat. No. 4,582,061 discloses a needle with ultrasonically reflective displacement scale, a puncturing device for insertion into the body, which has an ultrasonically coded displacement scale of gaseous inclusions regularly spaced along the length of the device. Owing to the acoustic reflectiveness of the gaseous inclusions, the precise location of the puncturing device can be directly and readily detected by an ultrasound visualization system. The acoustically reflective displacement scale enables the calibration of distances to be made directly from the ultrasound viewing screen. Located at the tip of the puncturing device is a gaseous inclusion which reveals the precise location of the tip of the device in the body.
In order to ultrasonically assess surgical treatments, some inventors have come up with different ideas. For instance, in U.S. Pat. No. 5,657,760, Ying et al. disclose an apparatus for ultrasonic Doppler monitoring of the extent and geometry of tissue damage resulting from thermal therapy. An embodiment of this invention comprises a laser fiber optic incorporated into an ultrasound transducer with the sound and laser beams collinear. As Doppler probe is collinear with fiber, in urologic laser treatments such as BPH, both probe and laser fiber (and endoscopic fiber) are inserted into the urethra. Cystoscopes usually also include a canal for flushing liquid into the urethral canal. Insertion of a device with several canals and apparatus into the urethra canal can cause a series of complications and may also make procedure more complex, requiring extreme care by physician. Furthermore, a special cystoscope for supporting numerous channels is needed, with a larger diameter than regular cystoscopes, thus causing an increased patient discomfort.
Those skilled in the art prefer images obtained by a probe inserted in a different angle such as those generated to diagnose prostate conditions. For example, transrectal ultrasound (TRUS) tests estimate the size of prostate gland and can be helpful in diagnosing or ruling out prostate cancer. After a lubricating gel is applied to rectum, the ultrasound probe, about the size and shape of a large cigar, is inserted for imaging the prostate and surrounding tissue. These ultrasound imaging procedures give important information on condition of the prostate and its anatomic surrounding, which is useful previous to the intervention. Furthermore, ultrasound imaging can give a physician valuable information during treatment especially when excessive bleeding, vaporization bubbles or anatomical structures at difficult angles of vision are present.
There is therefore a need for a laser treatment system that improves on the state of the art by allowing more precise and clear online view of treated area when maneuvering high power side firing laser beam transmission for eliminating abnormal soft tissue such as cancerous or hyperplasic prostate tissue. The present invention addresses this need.